Antigenic and genetic analyses of bluetongue viruses prevalent in Okayama prefecture [Japan]
2006
Fukutomi, T.(Okayama-ken. Government Office (Japan)) | Oouchi, M. | Sawada, K. | Hirai, N. | Hada, M. | Okuda, K.
Serological surveys from 1994 to 2004 revealed that Bluetongue virus (BTV) infection among sentinel calves had occurred in Okayama Prefecture in 1997, 1999, 2000, and 2001. BTV RNA segment 3 encoding the serogroup-specific VP3 was detected from blood cell samples obtained from seropositive sentinel calves in 1997 and 1999. Moreover, BTVs were isolated from three blood cell samples in 2001. Using cross-neutralization tests, the isolates had a different serological characteristic from the ON89-1 strain of BTV21 isolated in Japan. Neutralization tests and competitive ELISA with the isolate and ON89-1 strain were performed using the sentinel calf sera in 1997, 1999, 2000, and 2001. The results demonstrated that BTV prevalent in Okayama Prefecture in 1997 and BTV present in 1999 and 2001 had the same serological characteristic as the isolate different serological characteristics from the isolate and ON89-1 strain. Phylogenetic analysis revealed that the BTV gene detected in 1997 was on a different branch from those detected in 1999 and 2001. These results suggest that the spread of at least two distinct BTVs genetically and serologically different from the previous Japanese isolate has occurred in Okayama Prefecture during the eight years from 1997 to 2004.
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